Why Do USPS Certified Mail Letters Fail To Deliver
USPS has changed the way Certified Mail is handled - it is now mixed in with First-Class Mail which causes more work for the carrier. USPS even admits that its Certified Mail "service performance is lower than regular First-Clasee Mail® pieces... [due to] special handling" and then goes on to say in that same press release "Certified Mail® must be dispatched and handled in transit as First-Class Mail®." This literally explains why there are failures / refunds that result for some Certified Mail letters.